Social activism will definitely help to fight social challenges as when the whole society comes forward and stand against such challenges it makes the process of eradicating the problems and challenges of society easier. Social challenges are those challenges which the society face as a whole and these challenges are a problem for the whole society and not just a person.
The flow of individuals in and out of a population introduces new alleles and increases genetic variation within that population. Mutations are changes to an organism's DNA that create diversity within a population by introducing new alleles.
The tilt of the Earth is what causes the seasons...In the summer, the northern pole is pointed closer to the Sun giving the northern hemisphere more daylight hours. The opposite is true during the winter.
